Christopher Wellons (nullprogram.com, github.com/skeeto/) started using Emacs nine years ago and has built all sorts of nifty customizations since, including something that plays Tetris for you. He demonstrates the benefits of having an HTTP server running inside Emacs by using Skewer to interact with a web browser and Impatient-mode to share his syntax-highlighted buffer through the Web. In addition, he covers foreign function interfaces, packages, and other good things. Check it out!
Links:

Mickey Petersen chats about Mastering Emacs, learning advanced topics, navigating by expressions, and making the most of dired and shell. You can find him at masteringemacs.org or twitter.com/mickeynp
Transcript here!